I realise that I'm a bit late replying to this as you've already started your game but I enjoyed reading this thread and the 'patrons battle' and wanted to contribute. I've been playing a witch in the Kingmaker campaign and have just reached level 12 and the start of the penultimate chapter.
My witch ended up with the Occult patron list and to be honest my experience of the class has been that it doesn't actually make a huge amount of difference which patron list you chose other than for flavour. All the Patron lists will have spells that could be useful or useless at various points in the campaign so I picked a list that fitted my patron instead.
With regards to your choice of hexes, if you think Feral Speech fits the character go with it. I took that feat (mostly because it fitted with the character concept) and have found it very useful and flavoursome. In gameplay I have found the reality of the witch is that if I don't spend every round Slumber hexing everyone the rest of the party are disappointed (and its use can be pivotal in most battles). Hexes like Misfortune end up being rarely used as you spend each round putting people to sleep and often I don't even get to cast a single spell (not that my witch minds as she's bone-idle). For when you meet opponents immune to mind-effecting abilities Fortune or Healing comes in useful as you can help your comrades out instead or you finally get a chance to use some spells! I have found Evil Eye a useful hex too. I wouldn't bother with Misfortune again because I have found the Ill-Omen spell works just as well and doesn't take up a precious hex slot.
Finally my last tip for playing a successful witch in this (or maybe any) game is Use Magic Device and wands. The witch spell list can be quite limited and I think the witch is almost intended to make use of the skill to bolster her spell selection through trinkets and fetishes and wands. Also, those low level spells I wanted from other Patron lists I got as wands or scrolls and stocked up on a couple of wizard spells I wanted for flavour or utility to cover any gaps left by the rest of the party.
Hope this might help with your hex selection and I hope you enjoy playing your witch as much as I am!